Device for centering X-ray film cassettes

ABSTRACT

Cassette centering device for an X-ray cassette loading and unloading device using two parallelly movable guides engageable with the side edges of the cassette, the guides being movable by a lever arrangement driven by a motor, the lever arrangement including a link having two telescoping parts and biasing means constituting force absorbing means for cushioning the engagement of the guides with the cassette and compensating for motor overdrive.

TECHNICAL FIELD

This invention relates to a device for positioning X-ray film cassettesof different widths by means of two parallelly guided members movabletoward and away from each other in a cassette loading and unloadingapparatus.

BACKGROUND ART

A centering device of this general type is disclosed in U.S. Pat. No.3,150,263, issued Sept. 22, 1964 (FIG. 5). The centering device thereindisclosed comprises two pneumatically operated crank disks connectedtogether and rotating in opposite directions, each disk being associatedwith a guide by means of a pair of parallelly pivoted links.

In another cassette positioning device as disclosed in DE-OS 30 00 760,Offenlegungstag July 16, 1981, shifting movement of guide members isaccomplished by a motor driven worm gear.

Both of these prior devices are disadvantageous in that the centeringand alignment of a film cassette is effected by an abrupt and unabsorbedimpact of the guides against the side walls of the cassette.Furthermore, there is no provision for compensating for overtravel of anelectric motor in the second device. Moreover, in the case of thefirst-mentioned device, cassettes of larger sizes can only be preciselyand reliably aligned and centered by means of an additional slidingguide engaging the rear end of the cassette and transporting thecassette over the last portion of its path to the loading and unloadingstation.

DISCLOSURE OF THE INVENTION

The present invention provides a centering device of simple constructionthat is reliable and precise in operation, in which the impact of theguides against the edges of the cassette is attenuated and wherein themotor moving the bars is switched off at a given point and overtravel ofthe motor is compensated, such that undue pressure against the edges ofthe cassette is avoided.

Such operation is achieved by a lever arrangement for moving the guidemembers, said arrangement being actuated by a power driven linkpivotally attached to it and consisting of link portions movable withrespect to each other in a telescoping manner, with a force absorbingconnection between the link portions, for example, a spring, which urgesthe link portions to maximum extended position with respect to eachother.

In further detail, the link portions telescope together when the guidemembers abut against the edges of a cassette, the telescoping takingplace against the resistance of biasing means. The telescoping movementis arranged such that in a first section of this movement, control meansfor the power source is actuated, while continued movement to a secondsection compensates for overtravel of the power source.

As a result of this ingenious arrangement, the bias resisted telescopingof the link portions buffers the impact of the guide members against theedges of the cassette when aligning and centering takes place, yet thecassette is precisely aligned, free from play. The power source isswitched off while the guide members are still being shifted togetherand overtravel of the motor is compensated, thus avoiding clamping theguide elements too tightly against the cassette.

The guide members are conveniently made at least as long as a cassetteof maximum size, and the members are guided in their movement by a guiderod as well as guide rails. The free ends of the guide members extendinto the interior of the apparatus and are provided with guide grooves.

The invention is shown in a preferred embodiment in the appendeddrawings which are described below. In the drawings;

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 and 2 are plan views showing the apparatus in two functionalpositions;

FIG. 3 shows a detail of the construction in a sectional view along lineII--II;

FIGS. 4 and 5 are plan veiws corresponding to portions of FIGS. 1 and 2,respectively; and

FIG. 6 is a sectional view taken on line IV--IV of FIG. 4.

MODES OF CARRYING OUT THE INVENTION

Referring now to FIG. 1, there is shown apparatus 1 for unloading filmsheets from X-ray film cassettes of different sizes and loading suchcassettes with unexposed film. This invention is, of course, concernedonly with the cassette centering portion of such apparatus in the areaof the unloading and loading station. The centering device comprises twoparallelly guided members 10 and 12 movable toward and away from eachother. These members are located above a cassette transport belt 15which transports the cassette 19 (FIGS. 2 and 3) from an input point tothe loading and unloading station. The belt passes around two rollers14, one of which is driven. The cassette shown in the drawings issmaller than the maximum size that can be handled by this apparatus.

As can be seen from FIGS. 1-3, members 10 and 12, which we refer to asguide members, are attached to angle plates 11 and 13, respectively, bymeans of bolts 17. The respective angle plates 11 and 13 are movablymounted by means of guide sleeves 11a and 13a, respectively, on a guideshaft 16 secured between two mounting angles. The ends of members 10, 12which extend into the interior of the apparatus are provided with guidegrooves 10a and 12a (FIGS. 1 and 2). These guide grooves cooperate withguide rails 1b on an intermediate wall 1a of the apparatus, thusproviding additional guiding for the movement of members 10 and 12. Aguide ramp for the cassettes is indicated at 1e. It is located on theintermediate wall 1a. Two cassette abutments fastened to that wall areshown at 1d.

A symmetrical lever arrangement located between guide members 10 and 12serves to actuate said members. The lever arrangement consists of alever 6 pivoted centrally about a stationary pin 6c. At one free end 6a(FIG. 1), a first lever arm 7 is connected pivotally to lever 6. Arm 7extends to the right as viewed in FIG. 1 and is pivotally connected toangle plate 11 which supports guide member 10. At its other free end 6b,lever 6 is connected pivotally to a leftward extend lever arm 8, whichis pivotally connected to angle plate 13.

A drive motor 2 is mounted to an angle part 1c. A link consisting ofportions 4 and 5 transmits drive from the motor to the lever arrangementjust described. A crank disk 2a driven by the motor rotates in either oftwo directions indicated by the arrows A and B in FIGS. 1 and 2. End 4aof portion 4 of the link is pivotally attached to the crank disk. End 5aof portion 5 of the link is pivotally attached at the connection betweenlever 6 and lever arm 8.

As shown in some detail in FIGS. 4-6, the two portions 4 and 5 of thelink are linearly shiftable with regard to each other in a telescopingmanner. A motor controlling switch 3 is mounted on a central portion oflink portion 4. The portion of 4 to the right of the switch is U-shapedin cross section (FIG. 6) and slidably receives the left section ofportion 5. Two pin and slot arrangements provide a connection betweenportions 4 and 5. The slots are indicated at 5b and the pins at 18.

Biasing means in the form of spring 9 is connected at one end to atongue 4c of portion 4 and at the other end to a tab 5c on portion 5.Spring 9 biases the two portions 4 and 5 apart to the extended positionshown in FIG. 4 and constitutes force absorbing means which buffers thecassette engaging movement of the guide members 10, 12 and compensatesfor motor overtravel after the motor is switched off. In the extended,initial position of portions 4 and 5, a bent off portion 5c on the leftend of portion 5 rests loosely on the actuating button of switch 3.

When a cassette 19 is transported from the input point to the loadingand unloading station, motor 2 is switched on by switch means, notshown, when the leading edge of the cassette contacts one of theabutments 1d. The motor then rotates crank disk 2a in the direction Aand thereby moves link 4, 5 to the right to actuate lever arrangement 6,7, 8 to cause movement of guide members 10, 12 toward each other.

When guide members 10, 12 abut against the edges of a cassettepositioned between them, the slight resistance they thus encounterresists further movement of link portion 5 to the right, whereupon linkportion 4 begins telescoping movement with respect to portion 5 aspermitted by the pin and slot connection 5b, 18. This is accompanied bystretching of spring 9 and movement of switch 3 relative to portion 5through path section "a" as shown in FIG. 4. The actuating button of theswitch is thereby depressed by 5c and the motor is turned off.Overtravel of the motor, if not compensated, would cause guide members10, 12 to engage the cassette edges too firmly and distort it orinterfere with further operations on the cassette. Overtravel of themotor is compensated in a second path section "b" as shown in FIG. 4.Spring 9 and the pin and slot connection permit, yet buffer, furthermovement of link portion 4 during overdrive and also absorb the impactof guide members 10, 12 against the sides of the cassette.

While the invention has been described in connection with the handlingof X-ray cassettes, it will be understood that it is also applicable toother devices in which the same problems overcome by this invention, areencountered.

The invention has been described with reference to a preferredembodiment. However, it will be appreciated that variations andmodifications can be effected within the ordinary skill in the artwithout departing from the scope of the invention.

I claim:
 1. In an X-ray film cassette centering device of the poweroperated type in which guide members are movable in parallel toward andaway from each other to accommodate cassettes of different widths, theimprovement comprising:a lever arrangement operatively connected to saidguide members for accomplishing the parallel movement; and a linkmovable by a power source and operatively connected to said leverarrangement, said link comprising telescoping portions having forceabsorbing means operating when said portions are telescoped together. 2.A device as set forth in claim 1, wherein one of said link portionsincludes means for controlling the power source.
 3. A device as setforth in claim 1, wherein said force absorbing means comprises biasingmeans connecting the respective link portions.
 4. A device as set forthin claim 3, wherein said biasing means urges said link portions to theirfully extended positions.
 5. A device as set forth in claim 1, whereinthe power source is electric switch controlled and one of said linkportions carries means for operating said switch.
 6. A device as setforth in claim 5, wherein said electric switch is carried by one of saidlink portions and said means for operating the switch is carried byanother link portion.
 7. A device as set forth in claim 6, wherein saidswitch operating means is positioned to disable the power source as saidlink portions are telescoped together against the resistance of saidforce absorbing means.
 8. A device as set forth in claim 7, wherein saidswitch operating means is so positioned in relation to the switch andthe telescoping link portions are so dimensioned that in a first portionof the telescoping movement, the switch is operated to disable the powersource, and in a second portion of said movement, said force absorbingmeans compensates for overtravel of the power source.